WO2016142388A1

WO2016142388A1 - Pneumatic object provided with an elastomer layer sealed against inflation gases made of a thermoplastic elastomer in the form of a block copolymer

Info

Publication number: WO2016142388A1
Application number: PCT/EP2016/054936
Authority: WO
Inventors: Marc Greiveldinger; Emmanuel Custodero
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2015-03-09
Filing date: 2016-03-08
Publication date: 2016-09-15
Also published as: FR3033567A1; FR3033567B1

Abstract

The invention relates to a pneumatic object provided with an elastomer layer sealed against inflation gases, said elastomer layer comprising as, majority elastomer, a thermoplastic elastomer in the form of a block copolymer which includes: a) an elastomer block comprising at least units from isobutylene, and having a glass transition temperature no higher than -20 °C; and b) one or more thermoplastic blocks in the form of a statistical copolymer comprising units from at least one polymerisable monomer and units from β-pinene, the content of said units from β-pinene varying from 0.5 to 3 mol % relative to the number of moles of units of the block copolymer, and said block copolymer having a mean molecular weight of 120 to 220 kg/mol. The invention also relates to a method for sealing a pneumatic object against inflation gases.

Description

PNEUMATIC OBJECT WITH A HOLE

ELASTOMER SEALED WITH INFLATION GAS

OF A THERMOPLASTIC ELASTOMER IN THE FORM OF A

BLOCK COPOLYMER

The present invention relates to "pneumatic" objects, i.e., by definition, to objects which take their usable form when inflated with air or an equivalent inflation gas, and in particular to pneumatic tires.

More particularly, the present invention relates to a pneumatic lens provided with an elastomeric layer impervious to inflation gases, said elastomeric layer comprising as elastomer a thermoplastic elastomer in the form of a copolymer with particular bloks.

The invention also relates to a method for sealing a pneumatic object by means of the elastomeric layer impervious to inflation gases as defined above.

Finally, the invention relates to the use as a gas-tight layer for inflating, in a pneumatic object, an elastomeric layer as defined above.

In a conventional pneumatic tire of the "tubeless" type (that is to say without a tube), the radially inner face has an air-tight layer (or more generally any inflation gas) which allows the swelling to take place. and maintaining the pressure of the tire. Its sealing properties allow it to guarantee a relatively low rate of pressure loss, making it possible to maintain the swollen bandage in normal operating condition for a sufficient duration, normally of several weeks or several months. It also serves to protect the carcass reinforcement from the diffusion of air from the internal space to the bandage.

This function of inner layer or "inner liner" rubber is today filled with compositions based on butyl rubber (copolymer of isobutylene and isoprene), recognized for a long time for their excellent sealing properties.

However, a well-known disadvantage of butyl rubber-based compositions is that they exhibit significant hysteretic losses, moreover over a wide range of temperatures, a disadvantage which penalizes the rolling resistance of pneumatic tires.

Decreasing the hysteresis of these internal sealing layers, and ultimately the fuel consumption of motor vehicles, is a general objective facing current technology.

Thermoplastic elastomers of the SIBS (styrene-isobutylene-styrene) type have been developed in order to improve the hysteresis properties of the internal sealing layers containing them. We can notably mention the patent applications FR 08/57844 and FR 08/57845.

However, the use of SIBS based formulations as an internal sealant layer has disadvantages.

On the one hand, the SIB S internal sealing layers have a lack of adhesion to the other components of the pneumatic object and that both raw in the constitution of the tire and cooked with the carcass ply. Indeed, the absence of double bonds in the thermoplastic elastomer makes it insensitive to co-vulcanization with the carcass ply during cooking.

On the other hand, the pneumatic objects obtained from these thermoplastic elastomers have a limited heat resistance, which is expressed by the impossibility of removing the obj and pneumatic hot baking press without tearing material but also by the appearance of material creep in endurance tests from a thermomechanical point of view, such as high speed running tests.

There is therefore a need to develop new pneumatic objects based on a thermoplastic elastomer that can be used as an internal sealing layer. These pneumatic objects, while maintaining good sealing properties, must also have a good compromise in terms of adhesion and in terms of thermal resistance.

The Applicant has now surprisingly discovered that a particular thermoplastic elastomer in the form of a block copolymer which comprises an elastomeric block and one or more thermoplastic blocks in the form of a random copolymer of units derived from at least one monomer polymerizable and units derived from β-pinene, used as an elastomeric layer impervious to inflation gas in a obj and pneumatic, allowed to obtain a pneumatic obj and having a good seal to the inflation gases, as well as a good compromise in terms of adhesion of the elements of the objective and tire between them and in terms of thermal resistance.

The object of the invention is therefore to provide a pneumatic object provided with an elastomer layer which is impervious to inflation gases, said elastomer layer comprising as majority elastomer a thermoplastic elastomer in the form of a block copolymer which comprises:

a) an elastomeric block comprising at least units derived from isobutylene, and having a glass transition temperature of less than or equal to -20 ° C,

b) one or more thermoplastic blocks in the form of a random copolymer of units derived from at least one polymerizable monomer and units derived from β - pinene, the level of said β - pinene - derived units ranging from 0.5 to 3% in moles with respect to the number of units of the block copolymer,

and said block copolymer having a weight average molecular weight of from 120 to 220 kg / m 2.

The introduction of β - pinene and its particular content in particular make it possible to confer on the waterproof layer in the airfoil good adhesion properties both raw during the shaping and when cooked with the rubber components which make it are ac acents, especially with the carcass ply.

The particular content of β-pinene and the average molecular mass by weight of the copolymer with blocks in particular make it possible to to confer on the objective and the tire a good thermal resistance, in particular in order to prevent material being pulled out when the object is pneumatically dislodged from the baking press but also makes it possible to avoid material creep during its use, in particular during endurance tests from a thermomechanical point of view.

The invention also relates to a method for sealing a pneumatic object vis-à-vis the inflation gases, wherein is incorporated in said obj and pneumatic during its manufacture, or is added to said obj and tire after its manufacture, a elastomeric layer impervious to inflation gases as defined above.

Finally, the object of the invention is to use an elastomeric layer as defined above as a tire-tight layer in a pneumatic object.

The invention as well as its advantages will be readily understood in the light of the description, examples of embodiments which follow and the single figure which schematizes, in radial section, a tire according to the invention.

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight.

On the other hand, any range of values designated by the expression

"Between a and b" represents the range of values from more than a to less than b (i.e., limits a and b excluded) while any range of values referred to as "from a to b "Means the range of values from a to b (that is to say, including the strict limits a and b).

In the present application, the terms "block copolymer" and "thermoplastic elastomer" are equivalent.

In the present application, by "majority" designating an elastomer, is meant that this elastomer is the majority of all other elastomers present in the elastomeric composition or the elastomeric layer, that is to say that this elastomer represents more 50% by weight of all the elastomers present in the elastomeric composition or the elastomeric layer. In the present application, the term "part per cent elastomer" or "phr" means the part by weight of one component per 100 parts by weight of the elastomer (s), that is to say, the total weight of the elastomers, whether thermoplastic or non-thermoplastic. Thus, a 60 phr component will mean, for example, 60 g of this component per 100 g of elastomer.

By random copolymer consisting of units derived from at least one polymerizable monomer and units derived from β-pinene, it is meant that this copolymer consists of a random distribution of units resulting from at least one polymerizable monomer and from units derived from β-pinene.

By blo c in the form of a random copolymer, it is meant that this block comprises at least one sequence of 5 units, said sequence being a mixture of units resulting from at least one polymerizable monomer and units derived from β-pinene .

By elastomeric block is meant that this block comprises at least one sequence of 5 units derived from isobutylene.

Thus, a first object of the invention is a pneumatic lens provided with an elastomer layer that is impervious to inflation gases, said elastomer layer comprising as majority elastomer a thermoplastic elastomer in the form of a block copolymer which comprises :

The weight average molecular weight masses (Mw) and the number (Mn) of the block copolymer that can be used according to the invention can be determined, in a manner known per se, by GPC (for "Gel Permeation Chromatography").

The GPC unit comprises four modules: "Waters 717 plus autosampler", "Waters 5 15 HPLC pump", "Water 2487" and "Water 2414". A 0.05 ml solution sample is injected and passed through the columns (Shodex® GPC K-804 and Shodex® GPC K-802.5) using an eluent (chloroform) at a flow rate of 1.0 ml. / min at 35 ° C.

In the present invention, the glass transition temperature (denoted Tg) can be measured by the DMA (dynamic mechanical analysis) method of establishing the evolution curve of the elastic modulus G 'as a function of the temperature. According to this method, the glass transition temperature corresponds to the temperature at which the intersection between the line tangent to the vitreous plate and the line tangent to the transition zone between the vitreous plate and the rubber plateau is observed.

Thus, in the present description, unless expressly indicated otherwise, the glass transition temperature is defined as the temperature at which the intersection between the line tangent to the vitreous plate and the line tangent to the transition zone between the vitreous plate and the rubber plate, during the temperature sweep of a cross - linked sample (length of sample length: 6 mm, width: 5 mm, thickness: 2 mm) subjected to a sinusoidal solicitation (frequency of 10 Hz). As indicated above, this Tg is measured during the measurement of the dynamic properties, on a viscoanalyzer (DVA 200 - IT Instrumental Control), according to the JIS K 6384 standard (Testing Methods for Dynamic Properties or Vulcanized Rubber and Thermoplastic Rubber).

According to a first variant of the invention, the block copolymer has a linear diblo c structure, the elastomeric block being connected at one of its ends to a thermoplastic block.

According to a second variant of the invention, the block copolymer has a linear triblock structure, the elastomeric block being connected at each of its ends to a thermoplastic block. According to a third variant of the invention, the block copolymer has a star-shaped structure, the elastomeric block being central and being connected from 3 to 12 branches, each branch consisting of a thermoplastic block. Preferably, the number of branches of the block copolymer ranges from 3 to 6.

According to another variant of the invention, the block copolymer is in a branched or dendrimer form. The block copolymer is then composed of a branched or dendrimeric elastomer and a thermoplastic block, located at each end of the branches of the branched or dendrimeric elastomer.

The block copolymer preferably has a glass transition temperature (Tg, measured by DMA method) of less than -20 ° C, more preferably less than -40 ° C, and even more preferably less than -50 ° C. A value of Tg higher than these minima can reduce the performance of the waterproof layer during use at very low temperatures.

The block copolymer usable in the elastomeric waterproof layer of the objective and tire according to the invention has a weight average molecular mass ranging from 120 to 220 kg / m.sup.-1.

Preferably, the block copolymer has a weight average molecular weight of from 150 to 220 kg / m 2.

Even more preferably, the block copolymer has a weight average molecular weight of from 160 to 220 kg / m.sup.-1.

Below the minimum indicated, the cohesion between the chains of the elastomer may be affected. In addition, in this case, an increase in the use temperature may affect the mechanical properties, including the properties at break, resulting in decreased performance "hot".

Furthermore, a molecular weight that is too high can be penalizing for the implementation of the gas-tight layer, which can be difficult or impossible.

Thus, it has been found that a weight average molecular weight value in a range from 120 to 220 kg / mol is particularly well suited, especially when the block copolymer is used in an elastomeric layer impervious to inflation gases for a tire.

The block copolymer that can be used in the sealed elastomer layer of the pneumatic object according to the invention generally has a polydispersity index (Ip = Mw / Mn) less than or equal to 3, more preferably less than or equal to 2, and even more preferentially less than or equal to 1.5.

As a reminder, the block copolymer that can be used in the sealed elastomeric layer of the pneumatic object according to the invention comprises an elastomer block and one or more thermoplastic blocks.

The elastomer block of this block copolymer comprises at least units derived from isobutylene, and has a glass transition temperature of less than or equal to -20 ° C. (Tg, measured by DMA method).

Preferably, the elastomer block has a glass transition temperature of less than or equal to -40 ° C., preferably less than or equal to -50 ° C.

In a preferred variant of the invention, the elastomer block further comprises from 0.5 to 6% by weight, preferably from 1.5 to 5% by weight, relative to the total weight of the elastomeric block, of units derived from one or more conjugated dienes.

Conjugated dienes that can be copolymerized with isobutylene to form the elastomeric block are C ₄ -C ₁₄ conjugated dienes. Preferably, these conjugated dienes are chosen from among isoprene, 1,3-butadiene, 1-methylbutadiene, 2-methylbutadiene, 2,3-dimethyl-1,3-butadiene, 2,4-dimethylbenzene, 1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,3 1,3-diethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, 2,3-dimethyl-1,3-hexadiene, 2,4-dimethyl-1,3-hexadiene, 2,5-dimethyl-1,3-hexadiene, 2-neopentylbutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-vinyl-1,3-cyclohexadiene and their mixture. More preferably, the conjugated diene is isoprene or a mixture containing isoprene.

Advantageously, the elastomer block is halogenated.

This halogenation makes it possible to increase the firing rate of the elastomer layer comprising the block copolymer. This halogenation makes it possible to improve the compatibility of the bloated copolymer with the other elements constituting the elastomeric layer that is impervious to inflation gases. The halogenation is carried out in particular by means of bromine or chlorine, preferably bromine, on the units derived from conjugated dienes of the polymeric chain of the elastomeric block. Only a part of these units reacts with halogen. This portion of units derived from reactive conjugated dienes must nevertheless be such that the proportion of units derived from unreacted conjugated dienes with halogen is at least 0.5% by weight relative to the weight of the blo elastomer.

As explained above, the block copolymer usable in the elastomeric waterproof layer of the obj and tire according to the invention also comprises one or more thermoplastic blocks.

The thermoplastic block or blocks of this block copolymer are in the form of a random copolymer of units derived from at least one polymerizable monomer and units derived from β-pinene, the level of said units originating from β-pinene varying from 0.5 to 3% by moles relative to the number of units of the block copolymer.

In a preferred manner, the polymerizable monomer or monomers are chosen from styrene monomers.

By styrene monomer is meant in the present description, any monomer based on styrene, unsubstituted as substituted.

The following monomers may notably be mentioned: styrene, methylstyrenes and in particular Γ-methylstyrene, m-methylstyrene, p-methylstyrene, alpha-methylstyrene, alpha-2-dimethylstyrene and alpha-4-dimethylstyrene. and diphenylethylene; butylstyrenes, for example para-tert-butylstyrene; the chlorostyrenes for example Γο-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene and 2,4,6-trichlorostyrene; bromostyrenes, for example, o-bromostyrene, m-bromostyrene, p-bromostyrene, 2,4-dibromostyrene, 2,6-dibromostyrene and 2,4,6-tribromostyrene; fluorostyrenes e.g. Γο-fluorostyrene, m-fluorostyrene, p-fluorostyrene, 2,4-difluorostyrene, 2,6-difluorostyrene and 2,4,6-trifluorostyrene; and para-hydroxy-styrene.

Preferably, the styrenic monomer or monomers that may be used according to the invention are chosen from styrene, alpha-methylstyrene, diphenylethylene, p-methylstyrene, p-tert-butylstyrene, p-chlorostyrene and p-fluorostyrene.

The polymerizable monomer or monomers may also be chosen from indenic monomers.

By indene monomer is to be understood in the present description any monomer based on indene, unsubstituted as substituted. Among the substituted indenes may be cited for example alkyl indenes and aryl indenes.

As polymerizable monomers, mention may also be made of the following compounds and their mixtures:

acenaphthylene; those skilled in the art may, for example, refer to the article by Z. Fodor and J. P. Kennedy, Polymer Bulletin 1992 29 (6) 697-705;

isoprene, then leading to the formation of a number of 1,4-trans polyisoprene units and cyclized units according to an intramolecular process; those skilled in the art may for example refer to G. Kaszas, JE Puskas, P. Kennedy Applied Polymer Science (1990) 39 (1) 119-144 and JE Puskas, G. Kaszas, JP Kennedy, Macromolecular Science. Chemistry A28 (1991) 65-80;

esters of acrylic acid, crotonic acid, sorbic acid, methacrylic acid, acrylamide derivatives, methacrylamide derivatives, acrylonitrile derivatives, methacrylonitrile derivatives and their mixtures; there may be mentioned more particularly, adamantyl acrylate, adamantyl crotonate, adamantyl sorbate, 4-biphenylyl acrylate, tert-butyl acrylate, cyanomethyl acrylate, 2-cyanoethyl acrylate, 2-cyanobutyl acrylate, acrylate 2- cyanohexyl, 2-cyanoheptyl acrylate, 3,5-dimethyladamantyl acrylate, 3,5-dimethyladamantyl crotonate, isobornyl acrylate, pentachlorobenzyl acrylate, pentaflurobenzyl acrylate, pentachlorophenyl acrylate, pentafluorophenyl acrylate, adamantyl methacrylate, 4-tert-butylcyclohexyl methacrylate, tert-butyl methacrylate, 4-tert-butylphenyl methacrylate, 4-cyanophenyl methacrylate, methacrylate of 4-cyanomethylphenyl, cyclohexyl methacrylate, 3,5-dimethyladamantyl methacrylate, dimethylaminoethyl methacrylate, 3,3-dimethylbutyl methacrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, phenyl methacrylate, methacrylate i so-bornyl, tetradecyl methacrylate, trimethylsilyl methacrylate, 2,3-xylenyl methacrylate, 2,6-xylenyl methacrylate, acrylamide, N-sec-butylacrylamide, N-tert-butylacrylamide, Ν, Ν-diisopropylacrylamide, N-methylbutylacrylamide, N-methyl-N-phenylacrylamide, morpholylacrylamide, piperidylacrylamide, N-tert-butylmethacrylamide, 4-butoxycarbonylphenylmethacrylamide, 4-carboxyphenylmethacrylamide, 4-methoxycarbonylphenylmethacrylamide, 4-ethoxycarbonylphenylmethacrylamide, butyl cyanoacrylate, methyl chloroacrylate, ethyl chloroacrylate, isopropyl chloroacrylate, isobutyl chloroacrylate, cyclohexyl chloroacrylate, methyl fluoromethacrylate, methyl phenylacrylate, acrylonitrile , methacrylonitrile, and mixtures thereof.

In a particularly preferred manner, the polymerizable monomer is styrene.

As explained above, the thermoplastic block or blocks of this block copolymer are in the form of a random copolymer of units derived from at least one polymerizable monomer and units derived from β-pinene. The level of said units derived from β-pinene varies from 0.5 to 3% in terms of the number of units of the block copolymer.

Indeed, for a β-pinene level greater than 3%, the thermal resistance of the inflation gas-tight layer is degraded. On the other hand, for a β-pinene level of less than 0.5%, the beneficial effect of the presence of β-pinene in the inflation-gas-tight layer on the adhesion is practically not perceptible.

Preferably, the level of units derived from β-pinene ranges from 1 to 2.5% in moles, relative to the number of units of the block copolymer.

The thermoplastic block or blocks generally represent from 5 to 30% by weight, relative to the total weight of the block copolymer.

Preferably, the thermoplastic block or blocks represent from 10 to 20% by weight, relative to the total weight of the block copolymer.

In a first particularly preferred variant of the block copolymer that can be used according to the invention, that comprises:

b) one or more thermoplastic blocks in the form of a random copolymer of units derived from at least one polymerizable monomer and units derived from β - pinene, the level of said β - pinene units ranging from 1 to 2, 5% in moles with respect to the number of units of the block copolymer,

and said block copolymer having a weight average molecular weight of from 150 to 220 kg / m 2.

In a second particularly preferred variant of the block copolymer that can be used according to the invention, that comprises:

b) one or more thermoplastic blocks in the form of a random copolymer of units derived from at least one monomer polymerizable and units derived from β-pinene, the level of said units derived from β-pinene varying from 1 to 2.5% in moles relative to the number of units of the block copolymer,

and said block copolymer having a weight average molecular weight of from 160 to 220 kg / mol.

In a third particularly preferred variant of the block copolymer that can be used according to the invention, that comprises:

said block copolymer having a weight average molecular weight of from 150 to 220 kg / mol,

and said thermoplastic block or blocks representing from 10 to 20% by weight, based on the total weight of the block copolymer.

In a fourth particularly preferred variant of the block copolymer that can be used according to the invention, that comprises:

said block copolymer having a weight average molecular weight of from 160 to 220 kg / mol,

and said thermoplastic block or blocks representing from 10 to 20% by weight, based on the total weight of the block copolymer. The block copolymer which can be used according to the invention gives the inflation gas-tight composition which contains it a high adhesion capacity on the rubber components of the pneumatic object, in particular pneumatic tires, which are associated with it.

In addition, this block copolymer, despite its thermoplastic nature, gives the gas-tight composition which contains it a good hot cohesion of the material, especially at temperatures ranging from 150 to 200 ° C. These temperatures correspond to the cooking temperatures of tires. This high temperature cohesion permits hot stripping of these tires without altering the integrity of the gas-tight composition containing the particular block copolymer.

Also, the block copolymer that can be used according to the invention surprisingly makes it possible to satisfy a compromise of properties, often antinomic, of hot cohesion of the composition which contains it and of adhesion thereof to the rubber components adjacent thereto in the pneumatic object. This compromise of properties is achieved while maintaining the sealing properties and the processability of the composition comprising this block copolymer, as well as imparting improved hysteresis properties (compared with butyl rubber). as an inner tire liner.

The block copolymer that can be used in the hermetic impervious elastomer layer of the invention can be prepared by synthesis methods known per se and described in the literature, especially that mentioned in the presentation of the state of the art. of the present description. Those skilled in the art will be able to choose the appropriate polymerization conditions and regulate the various parameters of the polymerization processes in order to achieve the specific structural characteristics of the block copolymer that can be used according to the invention. In particular, several synthetic strategies can be implemented in order to prepare the block copolymer that can be used according to the invention.

A first strategy consists of a first step of synthesis of the elastomer block by living cationic polymerization of the monomers to be polymerized by means of a mono-functional, difunctional or polyfunctional initiator known to those skilled in the art, followed by the second synthesis step. thermoplastic block (s) by adding a mixture of at least one polymerizable monomer and a β-pinene monomer to the living elastomer block obtained in the first step.

Thus, these two steps are consecutive, which results in the sequenced addition:

monomers to be polymerized for the preparation of the elastomer block: isobutylene alone or mixed with one or more conjugated diene monomers;

monomers to be polymerized for the preparation of the thermoplastic block (s): one or more polymerizable monomers and β-pinene.

At each stage, the monomer (s) to be polymerized may or may not be added in the form of a solution in a solvent as described below, in the presence or absence of an acid or a Lewis base such as as described below.

Each of these steps can be carried out in the same reactor or in two different polymerization reactors. Preferably, these two steps are performed in a single reactor (synthesis "one-pot").

The living cationic polymerization is conventionally carried out by means of an initiator and optionally of a Lewis acid acting as co-initiator in order to form a carbocation in situ. Usually electro-donating compounds are added in order to give the polymerization a living character.

By way of illustration, the mono-functional, difunctional or polyfunctional initiators used for the preparation of the The block copolymer usable according to the invention may be chosen from (2-methoxy-2-propyl) benzene (cumylmethyl ether), (2-chloro-2-propyl) benzene (cumyl chloride), (2-hydroxy-2-propyl) -benzene, (2-acetoxy-2-propyl) -benzene, 1,4-di (2-methoxy-2-propyl) -benzene (or dicumylmethyl ether), 1,3,5-tri (2-methoxy-2-propyl) -benzene (or tricumylmethyl ether), 1,4-di (2-chloro-2-propyl) -benzene (or dicumyl chloride), 1,3,5-tri (2-chloro-2-propyl) -benzene (or tricumyl chloride), 1,4-di (2-hydroxy-2-propyl) -benzene, 1, 3, 5 - tri (2-hydroxy-2-propyl) -benzene, 1,4-di (2-acetoxy-2-propyl) -benzene, 1,3,5-tri (2-acetoxy-2-propyl) -benzene 2,6-dichloro-2,4,4,6-tetramethylheptane and 2,6-dihydroxy-2,4,4,6-heptane.

Preferably, dicumyl ethers, tricumyl ethers, dicumyl halides or tricumyl halides are used.

The Lewis acids may be chosen from metal halides of the general formula MXn where M is a member chosen from Ti, Zr, Al, Sn, P and B, X is a halogen such as Cl, Br, F or I and n is the oxidation state of the element M. Examples are TiCl _4, A1C1 _3, BC1 _3, BF _3, SnCl _4, PC1 _3, PC1 _5. The compounds TiCl ₄ , AlCl ₃ and BCl ₃ are used preferentially, and TiCl _{4 is} even more preferred.

The electro-donating compounds may be selected from known Lewis bases, such as pyridines, amines, amides, esters, sulfoxides and others. Among them are preferred DMSO (dimethylsulfoxide) and DMAc (dimethylacetamide).

The living cationic polymerization is carried out in an apolar inert solvent or in a mixture of polar and nonpolar inert solvents.

The apolar solvents which can be used for the synthesis of the block copolymer which can be used according to the invention are, for example, hydrocarbon, aliphatic, cycloaliphatic or aromatic solvents, such as hexane, heptane, cyclohexane and methylcyclohexane. , benzene or toluene. The polar solvents which can be used for the synthesis of the block copolymer which can be used according to the invention are, for example, halogenated solvents such as alkane halides, such as methyl chloride (or chloroform), ethyl chloride. butyl chloride, methylene chloride (or dichloromethane) or chlorobenzenes (mono-, di- or tri-chloro).

Those skilled in the art will be able to choose the appropriate temperature conditions in order to achieve the molecular weight characteristics of this copolymer.

A second synthesis strategy consists of preparing separately:

a telechelic or functional elastomer block at one or both chain ends by living cationic polymerization by means of a monofunctional, difunctional or polyfunctional initiator, optionally followed by functionalization reaction on the chain ends,

the living thermoplastic block or blocks, for example by anionic polymerization,

and then reacting the one and the other to obtain a block copolymer usable according to the invention. The nature of the reactive functions at each of the chain ends of the block and the proportion of living thermoplastic blocks relative to the blo c will be chosen by those skilled in the art for obtaining a block copolymer that can be used according to the invention.

The possible halogenation of the block copolymer that can be used according to the invention obtained according to one or the other of the synthetic strategies is carried out according to any method known to those skilled in the art, in particular those used for the halogenation of rubber. butyl and can be done for example by means of bromine or chlorine, preferably bromine, on the units derived from conjugated dienes of the polymeric chain of the elastomeric block, when they are present, or on the units derived from the β- pinene.

In certain variants of the invention according to which the block copolymer is starred or still connected, the processes described for example in the articles of Puskas J. Polym. Sci Part A: Polymer Chemistry, Vol. 36, pp. 85-82 (1998) and Puskas, J. Polym. Sci Part A: Polymer Chemistry, vol 43, pp 1 8 1 1 - 1826 (2005) can be implemented by analogy to obtain stellated, branched elastomeric central blocks or living dendrimers. Those skilled in the art will then be able to choose the composition of the monomer mixtures to be used in order to prepare the block copolymer that can be used according to the invention as well as the appropriate temperature conditions in order to achieve the molecular weight characteristics of this copolymer. .

Preferably, the preparation of the block copolymer that can be used according to the invention will be carried out by living cationic polymerization by means of a mono-functional, difunctional or polyfunctional initiator and by sequential addition of the monomers to be polymerized for the synthesis of the elastomeric block and the monomers to be polymerized for the synthesis of the thermoplastic block (s).

The present invention is not restricted to a specific polymerization process from such a monomer mixture. This type of process is known to those skilled in the art. Thus syntheses described in the prior art, in particular in patent documents EP 73 11 12, US 4 946 899, US 5 260 383, can be implemented by analogy to prepare the block copolymer used according to the invention.

The block copolymer alone can constitute the gas-tight elastomeric layer or be associated in this elastomeric layer with other constituents to form an elastomeric composition.

In particular, the block copolymer that can be used according to the invention can be in admixture with another block copolymer according to the invention of another type. For example, a first block copolymer according to the invention being in the form of a diblock, the elastomeric block being connected at one of its ends to a thermoplastic block, and a second block copolymer according to the invention being in the form of a diblock. a linear triblock, the blo c elastomer being connected at each of its ends to a thermoplastic blo c, both Block copolymers can then form a gas-tight elastomeric layer used according to the invention.

If any other elastomers are used in this composition, the block copolymer or copolymers that can be used according to the invention constitute the majority elastomer (s) by weight; they then represent more than 50%, more preferably more than 70% by weight of all the elastomers. Such minor complementary elastomers could be, for example, diene elastomers such as natural rubber or synthetic polyisoprene, butyl rubber or styrenic thermoplastic elastomers (TPS) other than the at least one block copolymer which can be used according to the invention. the limit of the compatibility of their microstructures.

As a TPS elastomer other than the block copolymer (s) usable according to the invention, mention may be made in particular of a TPS elastomer chosen from the group consisting of styrene / butadiene / styrene block copolymers, styrene / isoprene block copolymers. styrene, styrene / isoprene / butadiene / styrene block copolymers, styrene / ethylene / butylene / styrene block copolymers, styrene / ethylene / propylene / styrene block copolymers, styrene / ethylene / ethylene / propylene / styrene block copolymers and mixtures of these copolymers. More preferably, said optional additional TPS elastomer is selected from the group consisting of styrene / ethylene / butylene / styrene block copolymers, styrene / ethylene / propylene / styrene block copolymers and mixtures of these copolymers.

However, according to a preferred embodiment, the block copolymer or copolymers that can be used according to the invention are the only elastomers present in the gas-tight elastomeric layer.

Particularly preferably, the elastomeric airtight layer of the inflation gas comprises only one block copolymer usable according to the invention which is the only elastomer present in the elastomeric layer gas-tight. The previously described block copolymer alone is sufficient to fulfill the gas-tight function with respect to the pneumatic objects in which it is used.

However, according to a preferred embodiment of the invention, the latter is used in a composition which also comprises, as plasticizer, an extender oil (or plasticizing oil) whose function is to facilitate the setting particularly the integration in the pneumatic object by a lowering of the module and an increase in the tackifying power of the gas-tight layer.

Thus, in this preferred embodiment of the invention, the inflation-gas-tight elastomeric layer further comprises an extension oil.

As an extension oil, any extender oil, preferably of a slightly polar nature, capable of extending and plasticizing elastomers, in particular thermoplastics, may be used. At ambient temperature (23 ° C.), these oils, which are more or less viscous, are liquids (ie, as a reminder, substances having the capacity to eventually take on the shape of their containers), as opposed to in particular to resins or rubbers which are inherently solid.

Preferably, the extender oil is selected from the group consisting of polyolefinic oils (that is, derived from the polymerization of o-olefins, monoolefins or diolefins), paraffinic oils, naphthenic oils. (low or high viscosity), aromatic oils, mineral oils, and mixtures of these oils.

More preferably, the extender oil is selected from olefinic oils, and preferably is a polyisobutylene oil. (abbreviated as "GDP"). Indeed, this oil has demonstrated the best compromise properties compared to other oils tested, including a conventional oil paraffinic type.

By way of example, polyisobutylene oils are sold in particular by UNIVAR under the name "Dynapak Poly" (for example "Dynapak Poly 1 90"), by INEOS Oligomer under the name INDOPOL H 1200, by BASF under the names "Glissopal" (for example "Glissopal 1000") or "Oppanol" (for example "Oppano l B 12"); paraffinic oils are marketed for example by EXXON under the name "Telura 61 8" or by Repso under the name "Extensol 5 1".

The extender oil preferably has a number average molecular weight ranging from 350 to 4000 g / mol, more preferably from 400 to 3000 g / mol.

The number average molecular mass (Mn) of the extender oil, when present, can be determined by steric exclusion chromatography (SEC); the oil sample is previously solubilized in tetrahydrofuran at a concentration of about 1 g / l; then the solution is filtered through a 0.45 μιη porosity filter before injection. The apparatus used is a "WATERS alliance" chromatographic chain. The eluting solvent is tetrahydrofuran, the flow rate is 1 ml / min, the temperature of the system is 35 ° C and the analysis time is 30 min. A pair of two WATERS coils with the trade names "STYRAGEL HT6E" is used. The volume injected from the solution of the oil sample is 100 μΐ. The detector is a differential refractometer "WATERS 2410" and its associated software for the exploitation of chromatographic data is the "WATERS MILLENIUM" system. The calculated average molar masses relate to a calibration curve made with polystyrene standards.

Indeed, it has been shown that for medium molecular masses in numbers too low, there is a risk of migration of the oil outside the composition, while too high masses can lead to excessive stiffening of this composition. composition. This choice has proven to be an excellent compromise for the intended applications, particularly for use in a tire.

Preferably, the extender oil is present at a content greater than 5 phr, preferably between 5 and 100 phr. (parts by weight per hundred parts of total elastomer, that is to say the block copolymer usable according to the invention as well as any other elastomer present in the composition or elastomeric layer).

Below the minimum indicated, the elastomeric composition may have too high rigidity for certain applications while beyond the maximum recommended, there is a risk of insufficient cohesion of the composition and loss of tightness that can be harmful depending on the application.

For these reasons, in particular for use of the sealed composition in a tire, it is preferred that the extender oil content be greater than 10 phr, in particular between 10 and 90 phr, more preferably still than greater than 20 phr, in particular between 20 and 80 phr.

The inflation-gas-tight elastomeric layer described above may further include the various additives usually present in the elastomeric air-tightness layers known to those skilled in the art.

Examples include reinforcing fillers.

Any type of reinforcing filler known for its ability to reinforce a rubber composition that can be used for manufacturing tires, for example carbon black, a reinforcing inorganic filler such as silica, or a blend of these two types can be used. charge, especially a black carbon and silica blend.

Suitable carbon blacks are all carbon blacks, used individually or in the form of mixtures, in particular blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks). It is also possible to use, according to the targeted applications, blacks of higher series FF, FEF, GPF, SRF. The carbon blacks could for example already be incorporated into the diene elastomer in the form of a masterbatch, before or after grafting and preferably after grafting (see, for example, applications WO 97/36724 or WO 99/16600). As reinforcing inorganic filler other than carbon black, is meant by the present application, by definition, any inorganic or inorganic filler as opposed to carbon black, capable of reinforcing on its own, without other means than a coupling agent intermediate, a rubber composition for the manufacture of tires; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.

The physical state under which the reinforcing filler is present is indifferent, whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, reinforcing filler is also understood to mean mixtures of different reinforcing fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below.

As reinforcing inorganic fillers other than carbon black are especially suitable mineral fillers of the siliceous type, in particular of silica (SiO ₂ ), or of the aluminous type, in particular of alumina (Al ₂ O ₃ ).

Preferably, the level of reinforcing filler in the sealed elastomer layer varies from 10 to 200 phr, more preferably from 30 to 150 phr, in particular from 50 to 120 phr, the optimum being, in a manner known per se, different according to the particular applications targeted.

According to one embodiment, the reinforcing filler mainly comprises silica, preferably the level of carbon black present in the sealed elastomer layer being less than 20 phr, more preferably less than 10 phr (for example between 0.5 and 20 phr). pce, especially from 1 to 10 phr).

Preferably, the reinforcing filler predominantly comprises carbon black, or is exclusively composed of carbon black.

When the reinforcing filler comprises a filler requiring the use of a coupling agent to establish the bond between the filler and the elastomer, the sealed elastomeric layer comprises in in addition, in a conventional manner, an agent capable of effectively providing this link. When the silica is present in the impervious elastomer layer as a reinforcing filler, a bifunctional coupling agent (or bonding agent) is used in known manner in order to ensure a sufficient chemical and / or physical connection between the inorganic filler (surface of its particles) and the thermoplastic elastomer, in particular organosilanes or bifunctional polyorganosiloxanes.

In the impervious elastomeric layer that can be used according to the invention, the content of coupling agent preferably varies from 0.5 to 12 phr, it being understood that it is generally desirable to use as little as possible. The presence of the coupling agent depends on that of the reinforcing inorganic filler other than carbon black. Its rate is easily adjusted by the skilled person according to the rate of this charge; it is typically of the order of 0.5 to 15% by weight relative to the amount of reinforcing inorganic filler other than carbon black.

Those skilled in the art will understand that, as an equivalent load of the reinforcing inorganic filler other than carbon black, could be used a reinforcing filler of another nature, since this reinforcing filler would be covered with an inorganic layer such as silica, or would comprise on its surface functional sites, including hydroxyl, requiring the use of a coupling agent to establish the bond between the filler and the thermoplastic elastomer.

The waterproof elastomeric layer that can be used according to the invention may also contain reinforcing organic fillers that can replace all or part of the carbon blacks or other reinforcing inorganic fillers described above. Examples of reinforcing organic fillers that may be mentioned are functionalized polyvinyl organic fillers such as those described in applications WO-A-2006/069792, WO-A-2006/069793, WO-A-2008/003434 and WO-A- 2008/003435. As other additives usually present in the elastomeric layers impervious to inflation gases known to those skilled in the art, mention may be made, for example, of non-reinforcing or inert fillers, of coloring agents which can advantageously be used for the coloring of the composition, lamellar fillers further improving the seal (for example phyllosilicates such as kao lin, talc, mica, graphite, clays or clays modified ("organo clays"), plasticizers other than the above-mentioned extension oils, protective agents such as antioxidants or antiozonants, anti-UV, various processing agents or other stabilizers, or promoters able to promote adhesion to the rest of the structure of the obj and tire.

The gas-tight elastomeric layer previously described is a solid (at 23 ° C.) and elastic compound, which is particularly characterized, thanks to its specific formulation, by a very high flexibility and very high deformability.

According to a preferred embodiment of the invention, this elastomeric gas-tight layer has a secant modulus in extension, at 10% elongation (denoted M 10), which is less than 2 MPa, more preferably less than 1, 5 MPa (especially less than 1 MPa). This quantity is measured in first elongation (ie without accommodation cycle) at a temperature of 23 ° C, with a pulling speed of 500 mm / min (ASTM D412), and reported in section initial test piece.

The gas-tight elastomeric layer previously described can be used as a gas-tight layer in any type of objective and tire. Examples of such pneumatic objects include pneumatic boats, balls or balls used for sports or games.

It is particularly well suited for use as an airtight layer (or any other inflation gas, for example nitrogen) in a pneumatic object, a finished or semi-finished product, of rubber, especially in a pneumatic tire for motor vehicle such as a two-wheeled vehicle, tourism or industrial. Such an airtight layer is preferably disposed on the inner wall of the objective and pneumatic, but it can also be completely integrated into its internal structure.

The gas-tight layer preferably has a thickness greater than or equal to 0.05 mm, preferably ranging from 0.1 to 1 mm, and more preferably ranging from 0.1 to 2 mm.

It will be readily understood that, depending on the specific fields of application, the dimensions and the pressures, the embodiment of the invention may vary, the gas-tight elastomeric layer then having several preferential thickness ranges.

Thus, for example, for passenger-type tires, it may have a thickness of at least 0.4 mm, preferably between 0.8 and 2 mm. In another example, for pneumatic tires of heavy goods vehicles or agricultural vehicles, the preferred thickness may be between 1 and 3 mm. According to another example, for tire tires of vehicles in the field of civil engineering or for aircraft, the preferred thickness may be between 2 and 10 mm.

The objective and tire according to the invention is preferably a tire.

In general, the object and tire according to the invention is intended to equip motor vehicles tourism, SUV ("Sport Utility Vehicles"), two wheels (including motorcycles), aircraft, as well as industrial vehicles such as vans, trucks and other transport or handling vehicles.

As heavy goods vehicles, it will be possible to include subways, buses and road transport equipment such as trucks, tractors, trailers and off-the-road vehicles such as agricultural machinery or civil engineering.

The invention also relates to a method for sealing a pneumatic object and to the inflation gases, wherein is incorporated in said obj and pneumatic during its manufacture, or is added to said obj and tire after its manufacture, an elastomeric layer gas-tight inflation as defined above. Preferably in this sealing process, the elastomeric layer impervious to inflation gases is deposited on the inner wall of the object and pneumatic.

In a particular variant of this method, the objective and tire is a tire.

In this particular variant, during a first step, the inflation-gas-tight elastomeric layer is deposited flat on a manufacturing drum, before covering said inflation-gas-tight elastomeric layer with the remainder of the tire structure. .

The invention as well as its advantages will be understood more fully, in the light of the single figure which schematizes, in radial section, a tire according to the invention, as well as the following embodiments.

The single appended figure shows very schematically (without respecting a specific scale), a radial section of a tire according to the invention.

This tire 1 has a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a rod 5. The crown 2 is surmounted by a tread represented in this schematic figure. A carcass reinforcement 7 is wrapped around the two rods 5 in each bead 4, the upturn 8 of this armature 7 being, for example, disposed towards the outside of the tire 1 which is shown mounted on its j ante 9. The armature of carcass 7 is in known manner constituted by at least one sheet reinforced by so-called "radial" cables, for example textile or metal, that is to say that these cables are arranged substantially parallel to each other and s 'extend from one bead to the other so as to form an angle of between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is located halfway between the two beads 4 and passes through the middle of the crown reinforcement 6).

The inner wall of the tire 1 comprises an airtight layer 10, for example of a thickness equal to about 0.9 mm, on the side of the internal cavity 1 1 of the tire 1.

This inner liner (or "inner liner") covers the entire inner paro of the tire, extending from one side to the other, at least up to the jib hook when the tire is in the mounted position. . It defines the radially inner face of said tire intended to protect the carcass reinforcement from the diffusion of air coming from the inner space 1 to the tire. It allows inflation and pressure maintenance of the tire; its sealing properties must enable it to guarantee a relatively low rate of pressure loss and maintain the swollen bandage, in normal operating condition, for a sufficient period of time, normally several weeks or months.

In contrast to a conventional tire using a butyl rubber-based composition, the tire according to the invention uses in this example, as an inflation-gas-tight layer, a thermoplastic elastomer in the form of a block copolymer such as described above.

The tire provided with its airtight layer 10 as described above can be made before or after vulcanization (or baking).

Measurement methods

1) Tightness test

For this analysis, a rigid wall permeameter was used, placed in an oven (temperature 60 ° C in this case), equipped with a relative pressure sensor (calibrated in the range of 0 to 6 bar) and connected to a tube equipped with a valve inflation. The permeameter can receive standard specimens in the form of a disc (for example 65 mm in diameter in the present case) and with a uniform thickness of up to 1.5 mm (0.5 mm in the present case). The pressure sensor is connected to a National Instruments data acquisition board (four-way analog 0-10 V acquisition) which is connected to a computer performing a continuous acquisition with a frequency of 0.5 Hz (1 point every two seconds). The coefficient of permeability (K) is measured from the linear regression line giving the slope a of the pressure loss across the test piece as a function of time, after stabilization of the system, that is to say obtaining a stable regime in which the pressure decreases linearly with time. An arbitrary value of 100 is given for the airtightness of the control, a result greater than 100 indicating an increase in the airtightness and therefore a decrease in the permeability.

2) Adhesion test (or peeling): elastomeric layer impervious to inflation gases / layer based on a diene elastomer Adhesion tests (peel tests) were conducted to test the ability of the elastomeric waterproof layer to the gases to be adhered after curing to a layer of diene elastomer, more specifically to a conventional rubber composition for tire carcass reinforcement, based on natural rubber (peptized) and carbon black N330 (65 parts by weight for 100 parts of natural rubber), further comprising the usual additives (sulfur, accelerator, ZnO, stearic acid, antioxidant).

The peel test pieces (peel type at 1 80 °) were made by stacking a thin layer of gastight composition between two calendered fabrics first with SIB elastomer S (1.5 mm) and the other with the diene mixture considered (1.2 mm). A rupture primer is inserted between the two calendered fabrics at the end of the thin layer. The test piece after assembly was vulcanized at 180 ° C under pressure for 10 minutes. Strips 30 mm wide were cut with a cutter. Both sides of the fracture primer were then placed in the jaws of an Intron ® brand traction machine. The tests are carried out at ambient temperature and at a tensile speed of 100 mm / min. The tensile forces are recorded and these are normalized by the width of the specimen. A force curve is obtained per unit of width (in N / mm) as a function of the displacement of the moving beam of the traction machine (between 0 and 200 mm). The value of adhesion retained corresponds to the initiation of the rupture within the specimen and therefore to the maximum value of this curve.

An arbitrary value of 100 is given for the adhesion of the witness, a result greater than 100 indicating an increase in adhesion.

3) Thermal resistance test (or test for determination of a softening temperature)

To characterize the softening temperature of an elastomeric composition, the following test is used:

• Apparatus: dynamic mechanical analyzer (DMA Q 800) marketed by the company TA Instruments;

• Sample: of cylindrical shape, it is realized by means of a punch and measures on average 13 mm of diameter for a thickness of 2 mm;

• Solicitation: the sample holder is in the form of a compression jaw; this piece consists of a movable upper plate (1 5 mm in diameter) and a fixed lower plate (15 mm in diameter); the sample is placed between these two trays; the moving part makes it possible to apply a constraint defined on the sample, of IN; the assembly is placed in a furnace making it possible to carry out a temperature ramp from room temperature to 1 80 ° C. at 3 ° C./min during which the deformation of the sample is recorded; • Interpretation: the results are in the form of a sample deformation curve as a function of temperature; the softening temperature is considered as that for which the material has a decrease in its thickness of 10%.

An arbitrary value of 100 is given for the heat resistance of the control, a result greater than 100 indicating an increase in thermal resistance.

Example 1 Preparation of a Reference Block Copolymer (Polymer 1) - Styrene / Isobutylene / Styrene Block Copolymer

The block copolymer (polymer 1) is synthesized as follows: A 500 ml separable flask (polymerization vessel) is put under nitrogen, then n-hexane (molecular sieve dried, 23.8 ml) and butyl chloride (molecular sieve dried, 214.4 ml) are added by syringe. The polymerization vessel is then cooled by immersion in a dry ice / methanol bath at -70 ° C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (75 ml, 794 mmol), isobutylene is added to the polymerization vessel by means of a nitrogen pressure. Then, p-dicumyl chloride (0.1248 g, 0.540 mmol) and Γα-picoline (0.1026 g, 1.10 mmol) are added. Titanium tetrachloride (0.84 ml, 7.70 mmol) is then added to start the polymerization. After stirring for one hour at the same temperature (-70 ° C), a sample of the polymerization solution (about 1 ml) is extracted from the total polymerization solution.

Styrene (9.79 g, 94.1 mmol), previously cooled to -70 ° C, is then added to the polymerization vessel. 45 minutes after the addition of styrene, the polymerization solution is poured into hot water (500 ml) in order to stop the reaction and this mixture is then stirred for 30 minutes. Then, the solution of The polymerization is washed with deionized water (3 x 500 ml). The solvent and the analogs are evaporated from the washed reaction crude under reduced pressure at 80 ° C for 24 hours to obtain the block copolymer. The weight average molecular weight of the central block (polyisobutylene) and of the total block copolymer are measured by permeate gel chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. . These data are collated in Table I, hereinafter.

EXAMPLE 2 Preparation of a Comparative Block copolymer (Polymer 2) - Styrene-Pinene / Isobutylene Copolymer / Styrene-Pinene Copolymer of Low Molecular Weight

The block copolymer (polymer 2) is synthesized as follows: A separable flask (polymerization vessel) of 2 liters is put under nitrogen, then n-hexane (dried on molecular sieve, 107 ml) and butyl chloride (dried on molecular sieve, 959 ml) are added by syringe. The polymerization vessel is then cooled by immersion in a dry ice / methanol bath at -70 ° C. A Teflon supply tube is connected to a pressure - resistant glass bottle equipped with a three - way stopcock and containing isobutylene (300 ml, 3 1 8 1 mmol), isobutylene is added to the polymerization vessel by means of a nitrogen pressure. Then, p-dicumyl chloride (0.5000 g, 2.16 mmol) and α-pico line (0.41 g, 4.41 mmol) are added. Then, the titanium tetrachloride (3.38 ml, 30.8 mmol) is added to start the polymerization. After stirring for one hour at the same temperature (-70 ° C.), a sample of the polymerization solution (about 1 ml) is extracted from the total polymerization solution.

Successively, styrene (38.6 g, 335 mmol) and β-pinene (26.4 ml, 169 mmol), previously cooled to -70 ° C., are then added to the polymerization vessel. The conversion of styrene is followed by gas chromatography. After a rate of styrene conversion of 90% is achieved, the polymerization solution is poured into hot water (2 liters) in order to stop the reaction and this mixture is then stirred for 30 minutes. Then, the polymerization solution is washed with deionized water (3x 2 liters). The solvent and the analogs are evaporated from the washed reaction crude under reduced pressure at 80 ° C for 24 hours to obtain the block copolymer. The weight average molecular weight of the central block (polyisobutylene) and of the total block copolymer are measured by permeate gel chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I, hereinafter.

Example 3 Preparation of a Block Copolymer Usable in the Pneumatic Object According to the Invention (Polymer 3)

The block copolymer (polymer 3) is synthesized as follows: A separable flask (polymerization vessel) of 2 liters is put under nitrogen, then n-hexane (dried on molecular sieve, 192 ml) and butyl chloride (dried on molecular sieve, 768 ml) are added by syringe. The polymerization vessel is then cooled by immersion in a dry ice / methanol bath at -70 ° C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (175 ml, 1852 mmol), isobutylene is added to the polymerization vessel by means of a nitrogen pressure. Then, p-dicumyl chloride (0.1413 g, 0.611 mmol) and Γα-picoline (1.709 g, 18.3 mmol) are added. Then titanium tetrachloride (5.36 ml, 48.9 mmol) is added to start the polymerization. After stirring for 65 minutes at the same temperature (-70 ° C), a sample of the polymerization solution (about 1 ml) is extracted from the total polymerization solution. Then, the styrene is added (28.9 ml, 251 mmol). After the addition of styrene is complete, β-pinene (7.47 ml, 47.7 mmol) is added dropwise over 40 min. After the addition of β-pinene is complete, titanium tetrachloride (1.79 ml, 16.3 mmol) is again added and the mixture is stirred for 50 minutes. Afterwards, the polymerization solution is poured into hot water (2 liters) in order to stop the reaction and this mixture is then stirred for 30 minutes. Then, the polymerization solution is washed with deionized water (3x 2 liters). The solvent and the analogs are evaporated from the washed reaction crude under reduced pressure at 80 ° C for 24 hours to obtain the block copolymer. The weight average molecular weight of the central block (polyisobutylene) and of the total block copolymer are measured by permeate gel chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I, hereinafter.

Example 4 Preparation of a Block Copolymer Usable in the Pneumatic Object According to the Invention (Polymer 4)

The block copolymer (polymer 4) is prepared in the same manner as the block copolymer of Example 3 (polymer 3). The only difference is the amount of β-pinene used: 3.64 ml, 23.2 mmol.

The weight average molecular weights of the central block (polyisobutylene) and of the total block copolymer as well as the glass transition temperature are measured in the same manner as in Example 3. These data are collated in Table I, hereinafter .

Example 5 Preparation of a Block Copolymer Usable in the Pneumatic Object According to the Invention (Polymer 5) The block copolymer (polymer 5) is prepared in the same manner as the block copolymer of Example 3 (polymer 3). The only difference is the amount of monomer used: isobutylene (298 ml, 3161 mmol); styrene (49.5 g, 430 mmol); β-pinene (4.38 ml, 28 mmol).

The weight average molecular weight of the central block (polyisobutylene) and the total block copolymer as well as the glass transition temperature are measured in the same manner as in Example 3. These data are collated in Table I below. -after.

Table I

This table gathers the values of average weight masses by weight (Mw), the unit rates resulting from β-pinene in terms of the number of units of the block copolymer (% β-pinene) and the % by weight of the thermoplastic block (s) relative to the total weight of the block copolymer (% blo cs TP).

The resulting block copolymers (Polymers 1 to 5) were formulated in inflation gas-tight layers made of 100% block copolymer.

The sealed elastomeric thermoplastic layers of the invention are prepared in a conventional manner, for example by blending the copolymer into a twin-screw extruder, way to achieve the melting of the matrix, then use a flat die for producing the thermoplastic layer. More generally, the shaping of the thermoplastic can be made by any method known to those skilled in the art: extrusion, calendering, extrusion blow molding, inj ection, cast film ("cast film" in English).

The properties of these watertight layers were then evaluated.

The data are collated in Table II below. Table II

This table gathers the normalized values (with respect to layer 1) of the sealing, the adhesion and the thermal resistance of the elastomer layers prepared using the block copolymers previously synthesized above.

The elastomeric layers that can be used according to the invention

3 to 5) as well as the comparative elastomeric layer (layer 2) show a significant gain in adhesive performance compared to the reference elastomeric layer (layer 1).

However, considering all the performances (sealing, adhesion and thermal resistance), the comparative elastomer layer has sealing and holding performance. less thermal than the elastomeric layers used according to the invention.

Thus, the elastomeric layers that can be used according to the invention have a good compromise for the three properties referred to with respect to the comparative elastomeric layer.

Example 6: Other examples of waterproof layers used according to the invention. The block copolymers 3, 4 and 5 previously described are used to prepare gas-tight layers according to the invention (layers 6, 7 and 8).

These layers are prepared from the ingredients and contents of Table III below.

The sealed elastomeric thermoplastic layers of the invention are prepared conventionally, for example, by incorporating the various components into a twin-screw extruder, so as to effect the melting of the matrix and incorporation of all the ingredients, and then use a flat die for producing the thermoplastic layer. More generally, the shaping of the thermoplastic may be made by any method known to those skilled in the art: extrusion, calendering, extrusion blow molding, inj ection, cast film.

Table III

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Claims

1. Obj and tire provided with an elastomeric layer impervious to inflation gases, said elastomeric layer comprising as elastomer a thermoplastic elastomer in the form of a block copolymer which comprises:

a) an elastomeric block comprising at least units derived from isobutylene and having a glass transition temperature of less than or equal to -20 ° C,

2. Obj and according to claim 1, characterized in that the block copolymer has a linear diblock structure, the elastomeric block being connected at one of its ends to a thermoplastic block.

3. Obj and according to claim 1, characterized in that the block copolymer has a linear triblo c structure, the elastomeric blo c being connected at each of its ends to a thermoplastic blo c.

4. Obj and according to claim 1, characterized in that the block copolymer has a stellate structure, the elastomeric block being central and being connected from 3 to 12 branches, each branch consisting of a thermoplastic block.

5. Obj according to any one of the preceding claims, characterized in that the polymerizable monomer or monomers are chosen from styrene monomers, and preferably the po lymerizable monomer is styrene.

6. Object according to any one of the preceding claims, characterized in that the block copolymer has a weight average molecular weight ranging from 150 to 220 kg / mol.

7. Object according to any one of claims 1 to 5, characterized in that the block copolymer has a weight average molecular weight ranging from 160 to 220 kg / mol.

8. Object according to any one of the preceding claims, characterized in that the rate of units derived from β-pinene ranges from 1 to 2.5 mol%, relative to the number of moles of units of the block copolymer. .

9. Object according to any one of the preceding claims, characterized in that the thermoplastic block or blocks represent 5 to 30% by weight, relative to the total weight of the block copolymer.

10. Object according to any one of claims 1 to 8, characterized in that the thermoplastic block or blocks represent 10 to 20% by weight, relative to the total weight of the block copolymer.

11. Object according to any one of the preceding claims, characterized in that the elastomeric block has a glass transition temperature of less than or equal to -40 ° C, preferably less than or equal to -50 ° C.

12. Object according to any one of the preceding claims, characterized in that the elastomeric block comprises from 0.5 to 6% by weight of units derived from one or more conjugated dienes, preferably from 1.5 to 5%. by weight relative to the total weight of the elastomer block.

13. Object according to claim 12, characterized in that the conjugated dienes or dienes are chosen from isoprene, 1,3-butadiene, 1-methylbutadiene, 2-methylbutadiene, 2,3-dimethyl-1, 3- butadiene, 2,4-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl 1,3-dimethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, 2,3-dimethyl-1,3-hexadiene, 2,4-dimethyl-1,3-hexadiene, 2,5-dimethyl-1,3-hexadiene, 2-neopentylbutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-vinyl- 1,3-cyclohexadiene, and mixtures thereof.

An article according to any one of the preceding claims, characterized in that the inflation gas-tight elastomeric layer further comprises an extender oil.

An article according to claim 14, characterized in that the extender oil is selected from the group consisting of polyolefinic oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils, and mixtures thereof. oils.

An article according to claim 15, characterized in that the extender oil is selected from olefinic oils, and preferably is a polyisobutylene oil.

17. Object according to any one of claims 14 to 16, characterized in that the extension oil has a number-average molar mass ranging from 350 to 4000 g / mol, preferably ranging from 400 to 3000 g / mol. .

18. Object according to any one of claims 14 to 17, characterized in that the extension oil has a content greater than 5 phr, preferably between 5 and 100 phr.

19. Object according to any one of the preceding claims, characterized in that the elastomeric layer impervious to inflation gases has a thickness greater than or equal to 0.05 mm, preferably ranging from 0.1 to 10 mm, and more preferably ranging from 0, 1 to 2 mm.

20. Object according to any one of the preceding claims, characterized in that the elastomeric layer impervious to inflation gases is disposed on the inner wall of the pneumatic object.

21. Object according to any one of the preceding claims, characterized in that said object is a tire.

22. A method for sealing a pneumatic object with respect to the inflation gases, in which said pneumatic object is incorporated when manufactured, or added to said pneumatic object after its manufacture, an elastomeric layer impervious to inflation gases as defined in any one of claims 1 to 19.

23. The method of claim 22, characterized in that the elastomeric layer impervious to inflation gases is deposited on the inner wall of the obj and pneumatic.

24. The method of claim 22 or 23, characterized in that the obj and is a tire.

25. The method of claim 24, characterized in that during a first step, the elastomeric layer impervious to inflation gases is deposited flat on a forming drum, before covering said elastomeric layer impervious to the inflation gases. remainder of the tire structure.

26. Use as a gas-tight layer, in a pneumatic object, of an elastomeric layer as defined in any one of claims 1 to 19.